I don't know how this partition was created. Only I am using this computer, so I thought it is probably from some software program that I've installed. I've uninstalled all programs but this partition is still there, I still can't remove/format/delete it.

It is 300MB and as you can see in the picture it has some used space. But when I open it, it is empty.

No, i didn't install from MDT. Just i don't know when exaclty but short time after installation this appeared there and i can't remove it. @Phillip R. link tell same. I'll try just i can't reboot right now.
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Jason PaddleJun 18 '12 at 11:36

It's possible the partition was created during the OEM/system builder stage. Be sure you're not using BitLocker first!
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HaydnWVNJun 18 '12 at 11:45

How can i check if i use or not ? i just made step 1 and 2 from @speakr answer and will reboot later.
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Jason PaddleJun 18 '12 at 11:48

@JasonPaddle Open the Control Panel, then BitLocker Drive Encryption. If you use BitLocker, you will see the details there (example). Make sure that all your partitions/drives have BitLocker disabled.
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speakrJun 18 '12 at 11:52

@speakr I have only C:(wich is system) and D: second partition and they both are Off.
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Jason PaddleJun 18 '12 at 11:55